Offset litho process



OFF-SET LITHO PROCESS Filed Sept. '7. 1922 Opizcafly projecec mage fifi W- @ML 9.11.1,

www %W% 17211, @MV/L Patented Feb. 22, 1927.

UNITED STATES PATENT ',oFFlcE.

C. BEEBE AND ALEXANDER MURRAY, CINCINNATI, OHO, ASSIGNOBS T THE WADSWORTE WATCH CASE COMPANY, OF DAYTON, KENTUCKY, A CORPORA- TION OF KENTUCKY.

OFFSET LITHO PROCESS.

Application led September 7, 1922. Serial No. 586,796.

Qur invention relates to improvements in olf-set litho process and it more especially consists of the features hereinafter pointed out in the annexed claims.

The purpose of our invention is to provide steps for rapidly producing litho printing plates in connection with half tone negatives by transferring the soluble portions of a coating to a lithographic stone or plate; and

that thereafter subjects the transferred coating to a suitable cooperating medium for further treatment to produce a lithographic printing surface.

With these and other ends in view, we

set forth such instances of adaptation as will disclose the broad underlying features of our invention Without inthe broadest sense limiting ourselves to the rspecific details described herein.

Fig. 1 is a diagrammatic elevation in sec.- tion of a sensitive coating under the action of luminous rays.

Fig. 2 is a diagrammatic section showing` the unhardened portions of the coating re-` moved by a rubber transfer blanket.

Fig. 3 is also a diagrammatic elevation showing the unhardened areas transferred to a hygroscopic surface.

Fig. 4 shows the areas of Fig. 3 ina hardened state.

In practically carrying out our invention, we coat a. suitable surface 1 with alight sensitive medium 2 and optically project an image 3 Athereon consisting of maximum and minimum light areas so as to harden the coating at 4 under all the illuminated areas and retain it soluble or relatively soft under all the shaded areasA at 5. after which instead of washing out the soluble coating 5 as is usual in the direct production of printingsurfaces We place in contact with the exposed .coating a rubber blanket 6 to which the soluble part 5 of the coating adheres. The blanket 6 is then ace 7, such as a lithographic stone, or metal plate, under slight pressure so as to transfer the soft coating 5, which adheres to the rubber blanket 6, to the surface 7. After treatment in the usual lithographic manner the portions 5 become the hardened, ink receiving, parts 8 ready for duplication by printing.

Our process lends itself admirably for the laced in contact with a hygroscopic sur-4 vthe image may be represented by an irregular grain negative and it is immaterial whether the reproduction be enlarged more or less from the original, though for poster Work the ultimate screen pitch may be as 'coarse as twenty per inch.

We do ,not limit ourselves to the use of any specific coating media other than that such medium must be suiiciently sensitive to receive an optically projected image with relatively short exposures and that the coating shall become hardened under the action of light and remain soft in the shadows. The outstanding feature of our invention lies in bodily transferring the unacted u on coating 5 to a suitable lithographic sur ace Without any intervening treatment. However, it is possible that the transferred coating may be available for other reproduction processes which will obviously come within the spirit of our present invention.

vBy transferring the unacted upon portion 5 of the coating 2 to a hygroscopic surface and subsequently hardening the same at 8, it becomes possible to roll up such aA surface with fatty ink which will only adhere to the hardened or non-hygrosco ic transferred coating 8 and will be repelled y the adhering moisture of the hygrosco ic surface 7 as is well known in lithographic practice. It is understood that our process is equally applicable to the production of printing surfaces in one or any combination of colors made by color separation, negatives or otherwise.

Among various media the tung-oil varnish described in the coendin application, Ser. No. 542,124, ile Marc 8, 1922, by Murray C. Beebe, may be used. This application has matured into Patent Number 1,574,356 on Feb. 23, 1926.

What we claim is:

1. A reproductive rocess, consisting in coating a suitable sur ace with a light sensitive medium, in optically projecting an image on said surface to selectivel cause portions thereof to become partially msoluble and retain other portions thereof soluble, in transferringv the soluble portions of the coating to another surface, and in subsequently treating the transferred coating to harden the same and thereby produce a printable reproduction.

2. A reproductive process, consisting in preparing a suitable surface with a light sensitive coating adapted to become hardened under the action of light, in projecting an image on such coating said image consisting of cooperative opaque lines or dots having transparent areas therebetween that are optically impressed upon the coating to produce thereon inter-related hard and soft portions, in transferring the soft portions to a hygroscopic surface, and in subsequently causing said portions to become non-l1ygro scopic.

3. A reproductive process, consisting in optically projecting an image onto a sensi tive coating to thereby harden the portions of the coating covered by the luminous areas of the image leaving the other portions of the coating unhardened, and in transferring the unhardened portions of the coating to another surface.

4. A reproductive process` consisting in coating a suitable surface with a light sensitive medium, in projecting thereon an image composed of variable sized transparent and opaque areas so as to admit light through the transparent areas of the ima oe to harden the sensitive medium Without changing the unacted upon portions of the coating which is not subjected to the light, in transferring the unacted upon portions to a hygroscopic surface and in subsequently making said portions non-hygroscopic.

5. A photographie reproductive process, consist-ing in subjecting a sensitive coating to an image having separated luminous areas to thereby harden the coating and leave unhardened portions lying between which are inverselyr related to the hardened portions, in transferring the unhardened portions by means of a rubber blanket to a hygroscopic surface, and in subsequently hardening the transferred portions.

6. A photographic reproductive process, consisting in projecting on a light senstive coating an image the opaque areas of which causes the portions of the coating thereunder to remain in a soluble state, and in transferring the soluble portions ofthe coating to another surface without destroying the identity of said portions.

In testimony Whereotl we atlix our signatures.

MURRAY C. BEEBE. ALEXANDER MURRAY. 

